Dynamoelectric machine having a ventilation shield in the air gap



2 Sheets-Sheet 1 Dec. 22. 1953 1.. T. ROSENBERG ET AL DYNAMOELECTRIC MACHINE HAVING A VENTILATI SHIELD IN THE AIR GAP Filed June 20, 1952 o/MWMg w 2 t 8. n w 3 h 6 6 2 m e m W S n 2 A L I M E AVP A H G 6m RN E B H NW Emm SC .OML R E m TMS E L E O M A m D & 9 3 1 w 2 m 2 u 2 J w e n D F es mmw X03272 xii/4 *2: WW

Patented Dec. 22, 1953 DYNAMOELECTRIC MACHINE HAVYINGA VENTILATION SHIELD IN THE AIR GAP Leon '1. Rosenberg, Wauwatos'a, and John L.

Kuehlthau, Milwaukee, Wis., assignors to Allis- (Jhalmers Manufactur ng mpany, Milwaukee, Wis.

Application June 20, 1952, Serial No. 294,701

9 Claims.

This invention relates to the ventilation of a dynamoelect-ric machine, particularly to a cooling arrangement for a machine having radial ventilating passages in both the rotor and stator.

Present dynamoelectric machines have their power ratings limited by the cooling of the machine's. When rotor ventilating gas is discharged into the air gap to pass through radial ventilating passages in the stator core the efficiency of the stator cooling will decrease if the ventilating gas discharged from the rotor opposes the inward flow of stator ventilating gas or impinges on coil "sides of stator windings.

According to the present invention the rotor is cooled without decreasing the eflicien'cy of stator cooling by providing a shield between the stator passages and the rotor. I

It is therefore an object of the present invenion to provide a ventilating arrangement for a dynamoelectric machine having radial ventila ing passages in the rotor and in the stator so arranged that rotor cooling does not decrease the efficiency of the stator cooling. I

Another object of the invention is to provide a dynamoelectric machine in which hot ventilating gas discharged from the rotor passes radially through the stator without impinging on the side of a stator coil;

Another object of the invention is to provide a dynamoelectric machine in which rotor ventilating gas discharges through stator ventilating passages without opposing the flow of stator ventilating gas. v

Other objects and advantages will be apparout to one skilled in the art from the following description taken with the accompanying drawings, in which the figures are drawn on different scales. In the drawings:

Fig. 1 is a view partly in elevation and partly in longitudinal cross section of a dynamoelectric machine embodying the present invention;

Fig. 2 is a radial cross sectional view of a portion of the stator and rotor cores of the machine of Fig. 1 showing an air gap shield and (a ventilated rotor winding;

Fig. 3 is a view of a portion of the inner periphery oi the stator core including the air gap shield shown in Fig. 2;

Fig. 4 is a cross sectional view of a portion of the stator and rotor cores of another maehine embodyin the invention and sh wing an air can shield and longitudinal ventilating passages in the rotor core; and r Fi 5 i a plan view of a portion of the rotor coreshown in Fig. 4.

Referring to the drawing, the dynamoelectric machine shown in Fig. 1 is a totally enclosed hydrogen cooled turbogenerator. The ventilation arrangement therefor is shown and described in copending application of Sterling Beckwith, Serial No. 243,255, filed August 23, 1951. This ventilation arrangement is also applicable to dynamoelectric machines which are air cooled and which may have a housing open to the atmosphere. The turbogenerator shown comprises a rotating field member or rotor mounted on or integral with a rotatable shaft l i supported in suitable bearings, not shown. The rotor comprises a slotted mag netic core l2 provided with a field winding. The bearings support the rotor in coaxial relation with a stator with an air gap therebetween.

The stator is of conventional form and comprises an armature winding 14 supported in a slotted laminated magnetic core 15 mounted in a stationary support.

The stationary support comprises a cylindrical shell I6 which supports the stator core l5 through a cylindrical frame ll spaced from the shell. Radially rigid annular end plates l8 secure the ends of the frame and shell. Removable end bells I 9 are secured to the end rings and their central portions are provided with suitable shaft seals. The end bells, end rings, and shell are assembled to form a totally enclosed housing for the machine. The housing is normally fillable with ventilating gas such as hydrogen. Frame ['1 comprises apertured radial support plates 2| secured to the radially inner surface of the frame to support longitudinally extending bars 22 on which the stator laminations are assembled. Clamping members 23 hold the laminations in position.

Secured to the end portions of the frame between the end bells and the stator core are shields 24 or dished cross section extending inwar ly t ward the rotor shaft with their central portions extending axially inward to form housings or fans 26, 211 on the rotor shaft.

The frame includes longitudinal supply ducts 2.9 inserted in apertures in the radial plates 21 and he d in position thereby with the n er ed e o thedu ts secur d to the longitud nal bars 22- Thfl su pl 2 .3 p 3 1 11 1 11 ends 17. 9 n w th he spams b w en he s ields an the stator core around members 23. The supply ducts are also open on their radially inner side to connect with radial stator core ventilating passages 30, 3 I.

passages 30, .3! between groups. Each passage extends from the outer periphery of the core [5 to the air gap and is subdivided into inlet passages 32 and discharge passages 33 by spacer elements 3 secured to an adjacent lamination. Inlet passages 32 connect the supply ducts '29 with the air gap, and discharge passages 33 connect the air gap with the space between the stator core and frame ii and outside of supply ducts 29. The spacer elements above the tooth portion of the laminations are inclined in one direction with respect to a radial line in ventilating passages 30 and such spacer elements in the remaining alternate ventilating passages 3| are oppositely inclined. This effects a known spiral arrangement of the-spacer elements with the spiral reversed in adjacent radial ventilating passages 30, 3! to assure uniform cooling around the periphery of the stator core.

Ventilating gas from the discharge passages 33 moves circumferentially of the'stator core between the stator core [5, the supply ducts 29 and the frame I! and passes through longitudinal rows of apertures in the frame to the space between the frame and shell 16 and between a pair of coolers 36, 31.

Heat in the circulated ventilating gas is absorbed by coolers 36, 31 which are of generally conventional type disposed longitudinally in the space between the shell and the frame in the path of the circumferential travel of the ventilating gas. Four coolers may be used with pairs 9 of coolers 36, 3'! disposed on opposite sides of the 33, radially outward through these discharge passages 33 and radially through frame apertures to the space between the shell and frame and between a pair of coolers 36, 3?. Ventilating gas between the coolers divides and flows circumferentially in opposite directions through adjacent cool rs, then the ventilating gas again divides to flow axially to both ends of the housing,

' and then radially inward through ports 38 in the frame to the spaces confined between the end bells and the shields 24 back to the fans 26, 21 for recirculation through the machine. The stator core is provided with means comprising a shield 49 disposed in the air gap between the rotor and the stator in the region of the discharge of rotor ventilating gas into the air gap. This shield is secured to the inner periphery of the stator core in coaxial relation thereto. The shield 48 comprises bridges 4! which may be made of any suitable material such as a laminated synthetic resin. Bridges M are supported by adjacent stator slot wedges 2. The slot wedges 42 are suitably shaped for this purpose and provide grooves in their sides in which the bridges are wedged. Each bridge 4| has at least one longitudinal rib 43 which abuts one of the stator teeth.

Along the shield portion of the stator core, stator ventilating gas flows in inlet passages 32 to the air gap space between the shield 50 and the periphery of the stator teeth, then it flows only axially to an adjacent discharge passage 33 in the stator core. The bridges 4| are provided with openings such as drilled holes 44 which align only with the stator discharge ventilating passages 33. The holes are positioned adjacent to ribs d3 along the leading side thereof with respect to the direction of rotation of the rotor so that hot ventilating gas discharged from the rotor does not impinge on stator coil sides but impinges on ribs 43 and spacer elements 3d removed from the coil sides.

To increase the effectiveness of rotor ventilation the rotor windings are constructed and arranged in the slots of the rotor core 12 to provide axial ventilating ducts bringing the ventilating gas passing therethrough into direct contact with the metal of the winding conductors. The conductors 48 of the axially extending rotor winding have their end turns l'a' held in place at each end by a retaining ring 8 and an end plate 55 which together with the shaft and the end of the core define enclosed spaces 49, 5t confining the end turns 4?. As more fully explained below, ventilating gas is supplied to enclosed spaces 49, 58.

A suitable design and arrangement of the conductors 46 within the rotor slots is clearly shown in Fig. 2. The conductor are disposed insuperposed insulated relation within the straight walled slots. Each conductor has a substantially trapezoidal cross section. The adjacent conductors of a pair cooperate with the insulated walls of the slot to define therebetween a longitudinal ventilating duct 5! on opposite sides of the slot extending the length of the rotor core. These ducts are open at the ends of the slots to the enclosed spaces 59, 59.

Radial ventilating passages 52 connect the longitudinal ventilating ducts 5! with the air gap of the machine. The radial passages are located intermediate the ends of the slot portions of the rotor conductors and may be spaced throughout the length of the core or concentrated at the central portion thereof as shown in Fig. l. The radial passages 52 extend through the side portions of the conductors and the side portions of rotor slot wedges 53 and these passages are staggered on opposite sides of the slots.

The ventilating gas may be supplied to the rotor by means comprising a high pressure device such as the large diameter two stage centrifugal blower 55 shown mounted on the shaft at one end of the machine between an end bell I9 and fan 26. The blower 55 comprises first and second stage impellers 55, 5?. The inlet to the first impeller 56 is located centrally thereof along the shaft and adjacent fan 26. Ventilating gas from the blower i directed by suitable means to pressure chambers 58, 59 at opposite ends of the machine.

Such means may comprise any suitable duct arrangement; one such arrangement is shown and described in the above mentioned copending application of Sterling Beckwith. Such means connecting blower 55 to pressure chambers 58, 59 comprises a spiral or volute box 66 open on one side to receive ventilating ga discharged through port 6! from blower 55. Ventilating gas from volute box 68 passes through an end space enclosed by shell Iii, frame ll, an end plate [8, and by annular plate segment 62.

This end space is connected to a channnel 63 which is longitudinally disposed between shell and frame and extends the length of the machine between the rigid end rings. At the blower end of the housing a chimney E4 is connected to the channel 53 and lead radially'inward, proaooaeos footing through the volute box 60 to pressure chamber 58 enclosed by an end bell and the blower. A ressure chamber 59 is" similarly located at the other end or the machine and formed between an annular battle 65' and adjacent end bell [9. A chimney 66 connects the adjac'git end or the channel 63 to pressure chainbef 9.

Duct means for connecting the longitudinal ventilating ducts 5! in the rotor to the pressure chambers- 5'8, 59' may comprise axial ducts in the shaft it formed by flutes" GT in the shaft at both ends of the machine. At one end of the shaft the mounting for the blower 55' ran 26 encloses flutes t1 so the ducts formed thereby open only into pressure chamber 59 and into rotor one turn space 49 At the other end of the shaft, the mounting for fan 21 similarly encloses flutes 61 so theducts formed thereby open only into pros sure chamber so and into r'o'tor one turn space 50.

In the operation of the turbogenerator the blower'55 draws" ventilating gas from the coolers through ports 36 in name" I? through which ventilating gas is also drawn by fans 2'6, 21. An annular baffle plate 54 may be secured; to adjacent shield 2'4 and radially positioned in the space between the blower and shield to prevent suction created by the blower interfering with the flow of ventilating gas to fan 25. Ventilating gas enters blower 5'5 and is discharged therefrom througli port cl into the spiral duct and directed into the end space connected to chimney 54' to channel 53. One portion of the ventilating gas flows radially inward through chimney M to pressure chamber 58 at one end or the machine. The other portion of ventilating gas flows longitudinally of the machine through channel 53 and thence through chimney 65' radially inward to pressure chamber 59 at the other end of the machine; The-ventilating gas" in pressure" chambers 58,. 59 is at a relatively high pressure with respect to the pressure of the ventilating gas supplied to the stator by fans 26, 21.

Under such relatively high pressure, the ventilating gas flows from the pressure chambers axially through the shaft flutes 61 into the enclo-sed spaces 49, 56' where the rotor ens turns are exposed, thence into the end supply points of axial ducts 51 ad acent the rotor conductors where the gas flows at very high velocity longitudinally of the conductors and in direct contact therewith, thence radially through the rotor radial ventilating passages 52 and to the discharge points thereof into the air gap of the machine.-

The ventilating gas discharged from the rotor flows radially through holes 44 in bridges M to enter the discharge passages 33 which extend radially through the stator core. Due to the shielding provided by bridges H the ventilating gas discharged from the rotor does not oppose the inward flow of stator ventilating gas. This gas discharged from the rotor is guided by bridge ribs 43 and spacer elements 34' to pass through substantially only the middle portion of the discharge passage so that the not rotor gas cannot impinge on the stator coil sides.

After passing the tooth portion of the stator core the ventilating gases from fans 26, 21 and from blower 55 begin to mix. After passing through the stator core such gases mix further as they flow circumfer'enti'ally of the core to apertures in frame i1 between a pair of coolers, thence circumferentially in opposite directions through the coolers and through return ports 38 in frame 6 I"! back to blower 55 and to fans 26, 21 for we circulation through the machine.

Fig. 4 illustrates the application of the ventilation arrangement to a, machine like that shown in Fig. l but having a rotor cooled by ventilation through longitudinal ducts in the rotor. These ducts 68 are formed in a known manner such as by slotting the core and closing the slots by suitable wedges 69 which are spaced longitudinally from each other to provide radial discharge passages l4 therebetween connecting the longitudino.1 ducts G8 with the air gap intermediate the ends of the core. Y

The stator core ventilation may also be modiiie'd as shown in Fig. 4 in which the coaxi l shield comprises bridges 70 which have parallel longltudinal ribs H abutting stator teeth. The bridges 18 have openin 72 therethrough between the iongitudi'nalribs PI for receiving ventilating gas discharged from the rotor. These openings are aligned with stator discharge passages only. Spacer elements 34 are secured to the tooth portion of a lamination adjacent each radial ventilating passage 3!}, 3! to direct ventilating gas discharged from the rotor through substantially only the middle portion of the assages. Withopenings 72 between the pair of ribs H the ventilating gas discharged from the rotor will not impinge on a; coil side but on a rib H for either direction of rotation of the rotor. spacer elements i3 beyond the tooth portion of the stator passage are inclined in one direction with respect to a radial line in passages 38, and spacer elements '14 are oppositely inclined in passa es 3i.

Segregation or stator ventilating from rotor ventilation by use of the coaxial shields described is applicable to machines other than that shown. For example, the machines of Figs. 1 and 4 may omit the blower 5-5, spiral box and rotor end plates 45.

Fans 26, 2'! then circulate ventilating gas in arallel aths. One such path over the stator end turns as before to sup ly ducts 29 thence through the stator core to the air gap, and back through the stator core to the cooler and back to the fans. The other path is axially into the rotor, then radially out of the rotor through the air ga and through the stator to the coolers and back to the fans.

While but a few embodiments of the present invention have been shown and described, other embodiments will be apparent to one skilled in the art without departing from the spirit of the invention or the scope of the appended claims.

It is claimed and desired to secure by Letters Patent:

1. A gas cooled dynamoelectric machine comprising a cooler, a stator, a rotatable shaft, and a rotor mounted on said shaft, said rotor including a slotted core provided with an axially extending winding, said rotor winding comprising conductors constructed and arranged in said core slots to provide longitudinal ducts in said core, radial ventilating passages intermediate the ends of said rotor connecting said longitudinal duets with the air gap of said machine, said stator having radial inlet and discharge ventilating passages and an axially extending winding shield sccured to the inner periphery of said stator core in spaced coaxial relation thereto eifectively closing to gas discharged from said rotor said stator inlet passages which are substantially opposite said radial passages in said rotor, a centrifugal blower mounted on said shaft, duct means for leading gas from said blower to said 7 longitudinal ducts of said rotor, said blower causing said gas to flow through said d-uct means and axially through said longitudinal ducts in said rotor, thence radially through said radial passages in said rotor, said air'gap and said discharge passages in said stator, thence through said cooler and thence back to said blower, and a fan mounted on said shaft for forcing ventilating gas in a path over the end turn portions of said stator windings, thence radially inward through said stator inlet passages to the air gapof said machine, thence radially outward through said stator discharge passages.

2. A gas cooled dynamoelectric machine comprising a stator, a rotatable shaft, and a rotor mounted on said shaft, said rotor including a core having longitudinal ducts therein and radial ventilating passages intermediate the ends of said core connecting said longitudinal duets with the air gap of said machines, said stator having radial inlet and discharge ventilating passages and an axially extending winding, slot wedges securing said stator winding in the stator core slots, a shield secured to the inner periphery of said stator core in coaxial relation thereto, said shield comprising bridge members secured between adjacent slot wedges, said bridge members each having a longitudinal rib in engagement with a surface of said core, said bridge members having apertures aligned with said stator discharge passages to permit hot ventilating gas discharged from said rotor to enter only the discharge passages in said stator, said apertures being disposed in each said bridge member on the side of said rib with respect to the direction of rotation of said rotor so that ventilating gas discharged from said rotor is prevented by said rib in impinging on the portion of said stator winding within said discharge passage, fan means mounted on said shaft causing gas to flow through said longitudinal ducts in said rotor, thence through said radial passages in said rotor, said air gap and said discharge passages in said stator, and back to said fan means, and said fan means forcing ventilating gas in a path over the end turn portions of said stator winding, radially inward through said stator inlet passages to the air gap of said machine, axially between said shield and the periphery of said core and radially outward through said stator discharge passages.

3. A gas cooled dynamoelectric machine com prising a cooler, a stator, a rotatable shaft, and a rotor mounted on said shaft, said rotor including a core having longitudinal ducts therein and radial ventilating passages intermediate the ends of said core connecting said longitudinal ducts with the air gap of said machine, said stator having radial inlet and discharge ventilating passages and an axially extending winding, slot wedges securing said stator winding in the stator core slots, a, shield secured to the inner periphery of said stator core in coaxial relation thereto, said shield comprising bridge members secured bet-ween adjacent slot wedges, said bridge members each having a longitudinal rib centrally thereof in engagement with the surface of said core, said bridge members having apertures aligned with said stator discharge passages to permit hot ventilating gas discharged from said rotor to enter the discharge passages in said stator, said apertures being disposed in said bridge members on the leading sides of said ribs with respect to the direction of rotation of said rotor so that ventilating gas discharged from said rotor does not impinge on a side of said stator windings, a centrifugal blower mounted on said shaft, duct means for leading gas from said blower to said longitudinal ducts of said rotor, said blower causing said gas to flow through said duct means and axially through said longitudinal ducts in said rotor, thence radially through said radial passages in said rotor, said air gap and said discharge passages in said stator, thence through said cooler and back to said blower, and a fan mounted on said shaft for forcing ventilating gas in a path over the end turn portions of said stator windings, radially inward through said stator inlet passages to the air gap of said machine, axially between said shield and the periphery of said core and radially outward through said stator discharge passages.

4. A gas cooled dynamoelectric machine comprising a cooler, a stator, a rotatable shaft, and a rotor mounted on said shaft, said rotor including a slotted core provided with an axially extending winding, said rotor winding comprising conductors constructed and arranged in said core slots to provide longitudinal ducts bringing gas in direct contact with said conductors, radial ventilating passages intermediate the ends of said rotor connecting said longitudinal ducts with the air gap of said machine, said stator having radial inlet and discharge ventilating passages and an axially extending winding, slot wedges securing said stator winding in the stator core slots, a coaxial shield secured to the inner periphery of said stator core in coaxial relation thereto, said shield comprising bridge members secured between adjacent slot wedges, said bridge members each having a longitudinal rib in engagement with the surface of said core, said bridge members having apertures aligned with said stator discharge passages to permit hot ventilating gas discharged from said rotor to enter the discharge passages in said stator, said apertures being disposed in said bridge members on the leading sides of said ribs with respect to the direction of rotation of said rotor so that ventilating gas discharged from said rotor does not impinge on a side of said stator windings, a centrifugal blower mounted on said shaft, duct means for leading gas from said blower to said longitudinal ducts of said rotor, said blower causing said gas to flow through said duct means and axially through said longitudinal ducts in said rotor, thence radially through said radial passages in said rotor, said air gap and said discharge passages in said stator, thence through said cooler and back to said blower, and a fan mounted on said shaft for forcin ventilating gas in a path over the end turn portions of said stator winding, radially inward through said stator inlet passages to the air gap of said machine, axially between said shield and the periphery of said core and radially outward through said stator discharge passages.

5. A gas cooled dynamoelectric machine comprising a stator, and a rotor including a rotatable shaft, said rotor including a core having longi tudinal ducts therein and radial ventilating passages intermediate the ends of said core connect ing said longitudinal ducts with the air gap of said machine, said stator having radial inlet and discharge ventilating passages and an axially extending winding, a shield of nonmagnetic material secured to the inner periphery of said stator core in coaxial relation thereto effectively closing to gas discharged from said rotor said stator inlet passages which are substantially opposite said radial passages in said rotor and providing in said air gap segregated axial passageways between axially aligned ones of said inlet and discharge passages, fan means mounted on said shaft, means for guiding a flow of said gas from said fan means axially through said longitudinal ducts in said rotor, thence radially through said radial passages in said rotor, said air gap and said dist charge passa in d stator and back to Said t n means, a m ns for guidin her fl of said gas from said fan means in a path over the end turn portions of said stator windings, thence radially inward through said stator inlet passages to the air gap of said machine, thence axially through said passageways and radially outward through said stator discharge passages back to said fan means.

6. A gas cooled dynamoelectric machine comprising a cooler, a stator, a rotatable shaft, and a rotor mounted on said shaft, said rotor including a core provided with slots and with an axially extending winding, said rotor winding comprising conductors constructed and arranged in said core slots to provide longitudinal ducts in said core, radial ventilating passages intermediate the ends of said rotor connecting said longitudinal ducts with the air gap of said machine, said stator having radial inlet and discharge ventilating passages and an axially extending winding, a shield 01' nonmagnetic material secured to the inner periphery of said stator core in coaxial relation thereto effectively closing to gas discharged from said rotor said stator inlet passages which are substantially opposite said radial passages in said rotor and providing in said air gap segregated axial passageways between axially aligned ones of said inlet and discharge passages, fan means mounted on said shaft, means for guiding a flow of said gas from said fan means axially through said longitudinal ducts in said rotor, thence radially through said radial passages in said rotor, said air gap and said discharge passages in said stator, thence through said cooler and back to said fan means, and means for guiding another flow of said gas from said fan means in a path over the end turn portions of said stator windings, thence radially inward through said stator inlet passages to the air gap of said machine, thence axially through said passageways and radially outward through said stator discharge passages, thence through said cooler and back to said fan means.

'7. A gas cooled dynamoelectric machine comprising a stator and a rotor including a rotatable shaft, said rotor including a core having longitudinal ducts therein and radial ventilating passages intermediate the ends of said core connecting said longitudinal ducts with the air gap of said machine, said stator comprising a laminated core including spaced apart groups of laminations with each space between adjacent groups subdivided into inlet and discharge ventilating passages extending from the air gap of the machine to the periphery of the stator core, said stator core provided with an axially extending winding, a shield of nonmagnetic material secured to the inner periphery of stator core in coaxial relation thereto eiiectively closing to gas discharged from said rotor said stator inlet passages which are substantially opposite said radial passages in said rotor and providing in said air gap segregated axial passageways between axially aligned ones of said inlet and discharge passages, fan means mounted on said shaft, means for guiding a flow of said gas from said fan means axially through said longitudinal ducts in said, rotor, t ence radiany throu h said radial passages in said rotor, said air gap and said radial discharge passages in said stator and back to said fan means, and means for guiding another flow of said gas from said fan means over the end turn portions of said stator winding, thence radially inward through said stator inlet passages to the air gap of said machine, thence axially through said passageways and radially outward through said stator discharge passages back to said fan means.

8. A gas cooled dynamoelectric machine come prising a cooler, a stator, a rotatable shaft, and a rotor mounted on said shaft, said rotor including a core provided with slots and with an axially extending winding, said rotor winding comprising conductors constructed and arranged in said core slots to provide longitudinal ducts in said core, radial ventilating passages intermediate the ends of said rotor connecting said longitudinal ducts with the air gap of the machine, said stator cornprising a laminated core provided with an axially extending winding, said laminated core including spaced apart groups of laminations with each space between adjacent groups subdivided into inlet and discharge ventilating passages extending from the air gap to the periphery of said stator core, a shield of magnetic material disposed in the air gap and secured to the inner periphery of the stator core in coaxial relation thereto effectively closing to gas discharged from said rotor said stator inlet passages which are substantially opposite said radial passages in said rotor and providing in said air gap segregated axial passageways between axially aligned ones of said in let and discharge passages, fan means mountcd on said shaft, means for guiding a flow of gas from said fan means axially through said longitudinal ducts in said rotor, thence radially through said radial passages in said rotor, said air gap and said discharge passages in said stator, thence through said cooler and back to said fan means, and means for guiding another flow of said gas from said fan means in a path over the end turn portions of said stator windings, thence radially inward through said stator inlet passages to the air gap, thence axially through said passageways and radially outward through said stator discharge passages back to said fan means.

9. A gas cooled dynamoelectric machine comprising a stator and a rotor including a rotatable shaft, said rotor including a core having longitudinal ducts therein and radial ventilating passages intermediate the ends of said core connecting said longitudinal ducts with the air gap of said machine, said stator having radial inlet and discharge ventilating passages and an axially extending winding comprising a plurality of coils exposed to ventilating gas in said radial inlet and discharge ventilating passages, a pair of spacer elements radially disposed remote from adjacent said coils in each said discharge passage, a shield of nonmagnetic material secured to the inner periphery of said stator core in coaxial relation thereto effectively closing to gas discharging from said rotor said stator inlet passages which are substantially opposite said radial passages in said rotor and providing in said air gap segregated axial passageways between axially aligned ones of said inlet and outlet passages, said shield having apertures aligned with the spaces between said spacer elements in said discharge passages so that hot ventilating gas discharged from said rotor enters only the discharge passages in said stator and is prevented by said spacer elements from impinging on the sides of said coils, fan means mounted on said shaft, means for guiding a flow of said gas from said fan means axially through said longitudinal ducts in said rotor, thence radially through said radial passages in said rotor, said air gap and said discharge passages in said stator and back to said fan means, and means for guiding another flow of said gas from said fan means in a path over the end turn portions of said stator windings, thence radially inward through said stator inlet passages to the air gap of the machine, thence axially through said passageways and radially outward through said stator discharge passages back to said fan means.

LEON T. ROSENBERG.

JOHN L. KUEHLTHAU.

References Cited in the file of this patent UNITED STATES PATENTS Number 5 2,425,997

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